The invention generally relates to hermetic scroll compressors and more particularly to bearing lubrication systems in scroll compressors.
U.S. Pat. No. 5,306,126 (Richardson), issued to the assignee of the present invention, is incorporated herein by reference and provides a detailed description of the operation of a typical scroll compressor.
Typically, hermetic compressors of the scroll type including a scroll mechanism which receives refrigerant at a suction pressure, compresses the received refrigerant, and discharges the compressed refrigerant at an elevated discharge pressure. Such scroll compressors are typically used in refrigeration, air conditioning and other such systems. The typical scroll mechanism includes an orbiting scroll member and a fixed scroll member, but may in an alternative form comprise co-rotating scroll members. Wraps are provided on each of the scroll members and face and intermesh with each other in an orbiting fashion so as to form pockets of compression during compressor operation.
Scroll compressors take various forms, such as high-side type compressors, wherein the internal volume of the compressor housing, and the lubrication oil sump or reservoir therein, is primarily at discharge pressure. The crankshaft includes an axial oil conveyance passageway which extends into the sump and is in fluid communication with various lubrication points in the compressor mechanism. The axial oil conveyance passageway may extend into the sump through the crankshaft itself, or through a crankshaft extension which comprises an end of the crankshaft. Where the lubrication oil sump is at discharge pressure, oil may be forced upwards, through the oil conveyance passageway to the compression mechanism, at least partially by the influence of the discharge refrigerant gas pressure exerted on the surface of the oil in the sump. This, of course, requires some pressure differential between the oil in the sump and the oil delivered to the lubrication points. Oil pumps of various types, such as centrifugal or positive displacement, are also used to help force oil upwards from the sump, through the axial oil conveyance passageway in the crankshaft, to the lubrication points of the compressor mechanism.
It is usually desirable to provide a means of returning oil, once it has lubricated the compressor mechanism, immediately to the oil sump of the compressor assembly, rather than to allow the oil to be discharged with the compressed refrigerant from the compressor assembly, circulated with the refrigerant through the refrigerant system, and returned to the compressor from the refrigerant system with the suction pressure gases. Oil so circulated coats the interior surfaces of heat exchangers, decreasing their efficiency, and may become logged for a substantial time in refrigeration system components before being returned to the compressor's oil sump. It is, however, desirable to provide some amount of oil to the interleaved scroll wraps to lubricate and help seal them. Oil provided to the space between the interleaved scroll wraps is usually carried from the compressor assembly with the compressed gas. A passage through which a small amount of oil is provided to the interleaved scroll wraps, but while preventing substantial amounts of oil from being discharged with compressed gas from the compressor assembly, is desirable. It is also desirable to return oil, after it has lubricated the various lubrication points of the compressor mechanism, to the oil sump for immediate reuse.
Further, there are certain circumstances, such as immediately upon compressor startup, when the pressure of refrigerant between the interleaved scroll wraps is at a pressure higher than discharge pressure. Refrigerant gas may vent from between the interleaved scroll wraps through portions of the lubrication system which are ordinarily under discharge pressure. Because oil may be carried away from lubricated surfaces by refrigerant, it is desirable to provide a flowpath for refrigerant venting from the space between the interleaved scroll wraps, through the above-mentioned passage, to the discharge pressure chamber of the compressor assembly, which does not cause the refrigerant to flow through bearings, which may flush the oil therefrom.